In recent years, EHC (electrically heated catalyst) devices have been attracting attention as an exhaust purification device that purifies exhaust gases discharged from engines of automobiles and the like. In EHC devices, it is possible to enhance the efficiency of the purification of the exhaust gas by electrically heating and forcibly activating a catalyst even under the conditions in which the temperature of the exhaust gas is low and hence the catalyst cannot be easily activated, such as immediately after the engine is started.
In an EHC device disclosed in Patent Literature 1, on the outer circumferential surface of a cylindrical catalyst support having a honeycomb structure on which a catalyst such as platinum and palladium is supported, surface electrodes extending in the axial direction of the catalyst support are formed. Further, comb teeth-like wiring lines are connected to the surface electrodes and an electric current is feed therethrough. This current spreads in the catalyst support axial direction in the surface electrodes and hence the entire area of the catalyst support is electrically heated. In this way, the catalyst supported on the catalyst support is activated, and unburned HC (hydrocarbon), CO (carbon monoxide), NOx (nitrogen oxide) and so on contained in the exhaust gas that passes through the catalyst support are removed by the catalytic reaction.